A combined bottling plant includes a number of cooperating processing machines, performing a number of corresponding operations, such as (but not limited to) forming, filling, sterilising, labelling and capping of containers, for example plastic bottles.
Each machine generally includes a main rotating wheel (or carousel), carrying along its periphery a number of processing units performing processing operations on a respective number of containers.
The various processing machines are arranged in a desired operating sequence, at a close distance one with respect to the other, and conveying or transfer assemblies, each including a number of transfer star wheels or analogous conveying elements, allow transfer of the containers between the various processing machines, through the required operating sequence.
During regular operation, it is required to achieve synchronization between the rotary motions of two or more machines in the processing plant, e.g. the blowing and filling machines, meaning that the machines are operatively coupled to operate in synchronization with respect to their rotary position around a respective axis of rotation and the speed of rotation expressed as number of containers processed per unit time.
A known solution for achieving synchronization is diagrammatically depicted in FIG. 1, which shows a container-processing plant 1 including: a container-forming machine, e.g. a blowing machine 2; and a processing machine, e.g. a filling machine 4, operatively coupled to the blowing machine 2 to fill containers that have been previously formed by the same blowing machine 2.
Blowing and filling machines 2, 4 include: a respective main rotating wheel (or carousel) 5, carrying (in a manner not shown) a number of processing units designed to perform processing operations on a corresponding number of containers; a respective electric motor 6, in particular an asynchronous electric motor, designed to cause rotation of the respective rotating wheel 5 via a rotating shaft 7; and a respective control unit 8, including a PLC (Programmable Logic Controller) 9 or similar computing unit, operatively coupled to the respective electric motor 6 and providing suitable control and power supply signals thereto, in order to control the rotary motion of the respective rotating wheel 5.
In particular, for synchronization of their rotating motion, blowing and filling machines 2, 4 further include: a respective sensing wheel 10, having a toothed rim, arranged below the rotating wheel 5 and coupled to the same rotating shaft 7 so as to rotate therewith; and a respective synchronization optical sensor 11, in particular a photocell sensor, operatively coupled to the sensing wheel 10.
The synchronization optical sensors 11 of the blowing and filling machines 2, 4 are configured to generate a respective pulse-train synchronization signal S1, S2, wherein each pulse corresponds to detection, by the respective sensor, of a tooth of the respective sensing wheel 10 during rotation of the same sensing wheel 10.
The synchronization signals S1, S2 are received by a synchronization module 12 of the control unit 8 of the filling machine 4, which is programmed to process the same synchronization signals S1, S2 and to control the respective electric motor 6 to achieve synchronization with the motion of the blowing machine 2. In particular, the synchronization module 12 suitably modifies the speed of the rotary motion of the respective rotating wheel 5, until the pulses in the synchronization signals S1, S2 are synchronized (i.e. until the edges, e.g. the rising edges, of corresponding pulses of the synchronization signals S1, S2 occur substantially at a same instant of time).
According to this solution, the synchronization process requires motion of both machines, blowing and filling machines 2, 4, at a synchronization speed, whose value is suitably set so as to achieve a sufficient resolution of the synchronization optical sensors 10; this synchronization speed is lower than a full operating speed of the rotating wheels 5, at which the blowing and filling machines 2, 4 are configured to perform the respective forming and filling operations on the preforms/containers.
The present Applicant has realized that the above synchronization solution has some drawbacks, which do not allow to fully exploit its advantages, in particular in case of faults in the container-processing plant 1. Faults that may occur during operation are e.g. formation of defective containers, or destroying of containers due to an excessive pressure applied during the filling operations or due to defects in the formation of the same containers.
In the event of a fault occurring in the processing plant 1, operation of the blowing and/or filling machine 2, 4 is interrupted, in order to address and solve the issue. Once the fault is removed, operation of the blowing and/or filling machine 2, 4 is resumed and synchronization between the same blowing and/or filling machine 2, 4 has to be once again achieved.
The present Applicant has realized that using the above discussed solution entails a rather long time for achieving synchronization, in particular due to the fact that: if the filling machine 4 is stopped, at the restart of the operation, the blowing machine 2 has to slow down to the synchronization speed, at which synchronization may be achieved, before the speed ramps up to the full operating speed for both blowing and filling machines 2, 4; conversely, if the blowing machine 2 is stopped, also the filling machine 4 is stopped, and, at the restart of the operation, both the filling and the blowing machines 2, 4 have to reach the synchronization speed, so as to achieve synchronization, before the speed may ramp up to the full operating speed for both machines.
The need is therefore felt for a synchronization solution allowing to achieve a more efficient synchronization between the machines in the container-processing plant, in particular allowing to decrease the time needed for the synchronization process, particularly at restart of the processing operations after a fault has occurred.